Effect of Sealing Greases on Inhibiting the Leakage of Supercritical CO2: A Molecular Dynamics Study

This work investigates the effect of sealing grease on inhibiting the leakage of supercritical carbon dioxide (CO2) using molecular dynamics simulation. Consideration is given to the effects of temperature, pressure, and leakage channel height. It is found that CO2 primarily leaks by diffusing into the interface between the grease and the channel at low temperatures, but the leakage is dominated by interfacial diffusion and the bulk penetration of CO2 across the greases at high temperatures. Moreover, the presence of a large amount of supercritical CO2 at the interface weakens the interactions between the grease and the channel, resulting in the extrusion of greases at high temperatures. For the pressure effect, the leakage always happens through interfacial diffusion with a low or high pressure. The high pressure can cause the extrusion of greases, as CO2 distributed in both the interface and the grease can enhance its fluidity and make it more likely to be extruded from the channel under high pressure. Finally, leakage primarily involves interfacial diffusion for a small channel height, but it is also dominated by such diffusion and bulk penetrations with a large height, which is due to the boundary effect on the fluidity of greases.